Rand Paul, R-Ky., on Sunday became the first senator known to have tested positive for COVID-19.
"Senator Rand Paul has tested positive for COVID-19," Paul's account tweeted. "He is feeling fine and is in quarantine. He is asymptomatic and was tested out of an abundance of caution due to his extensive travel and events. He was not aware of any direct contact with any infected person."
"He expects to be back in the Senate after his quarantine period ends and will continue to work for the people of Kentucky at this difficult time," the thread continued. "Ten days ago, our D.C. office began operating remotely, hence virtually no staff has had contact with Senator Rand Paul."
Paul's chief of staff later clarified that he "decided to get tested after attending an event where two individuals subsequently tested positive for COVID-19, even though he wasn't aware of any direct contact with either one of them."
Sen. Jerry Moran, R-Kan., told colleagues at Sunday's policy meeting that he saw Paul at the Senate gym earlier in the day, his communications director confirmed on Twitter.
Paul's account later tweeted that he visited the gym before he found out he had tested positive.
Paul is the third member of Congress to announce a positive test for the coronavirus, following Reps. Mario Diaz-Balart, R-Fla., and Ben McAdams, D-Utah. Several Republican lawmakers also self-quarantined this month after they learned that they had interacted with someone who tested positive for the virus at the Conservative Political Action Conference.
The White House said President Donald Trump, who attended CPAC and also interacted with multiple people at his Florida resort who later found out they were infected, tested negative for the virus.
In an interview with NBC News, Diaz-Balart said Saturday that he is feeling better after a week but that the initial symptoms hit him "like a ton of bricks." McAdams, meanwhile, said on NBC News' "Today" last week that the symptoms "felt like I had a belt around my chest, and so I couldn't breathe deeply."
Paul, a libertarian-leaning physician, forced a delay on the Senate's first coronavirus aid bill by pushing a doomed amendment. He later voted against it.
Paul's diagnosis has triggered a discussion about whether senators, many of whom are in older age brackets, should go home immediately or self-quarantine, given their likely contact with Paul, who was on the Senate floor extensively over the last week.
The news created fresh uncertainty about how Congress can finish and pass emergency coronavirus legislation, on which Democrats and Republicans are still struggling to reach a deal.
Sens. Mike Lee and Mitt Romney, both Utah Republicans, were the first two lawmakers to say they would be self-quarantining for two weeks after having had "extended" interactions with Paul and would have to miss floor votes.
Speaking at the White House coronavirus task force press conference on Sunday, Trump offered well wishes, saying "I want to just say that Senator Rand Paul a friend of mine, he has been a great friend of mine, always there when we needed him, when the country needed him." Trump said that he and Paul have not had any recent in-person interactions.
When Trump was told Romney was also in quarantine, he said sarcastically, "Romney’s in isolation? Gee, that’s too bad."
Sen. Kyrsten Sinema, D-Ariz., criticized Paul in a tweet, calling his gym visit "absolutely irresponsible."
"You cannot be near other people while waiting for coronavirus test results," she wrote. "It endangers others & likely increases the spread of the virus."
Download the NBC News app for full coverage and alerts about the coronavirus outbreak
Paul suffered lung damage as a result of having his ribs broken during an altercation with a neighbor in 2017. Last year, he had part of his lungs removed. Paul's chief of staff told NBC News that the surgery puts the senator "in a higher-risk category as it relates to pulmonary issues."
His father, former Rep. Ron Paul, R-Texas, who is also a doctor, last week referred to the coronavirus crisis as a "hoax." The pandemic has infected more than 300,000 people worldwide, according to Johns Hopkins University.